Im Rahmen des Forschungsvorhabens wurden 122 AU-auffaellige Fahrzeuge mit Ottomotor und geregeltem Katalysator weitergehend untersucht. Die Fahrzeugauswahl an den Pruefbahnen erfolgte nach den Hauptkriterien Abgasuntersuchung (AU) "nicht bestanden" und der Hubraumklasse sowie dem Zulassungsjahr. Um die Wirksamkeit der AU darzustellen, wurden die defekten Fahrzeuge im Anlieferungszustand in drei verschiedenen Fahrzyklen auf der Rolle vermessen, anschliessend in markengebundenen Fachwerkstaetten instand gesetzt und nach bestandener AU wiederum auf der Rolle vermessen. Der Vergleich der Abgas-Emissionen vor und nach der Reparatur im NEFZ-Zyklus zeigt fuer die untersuchten Fahrzeuge eine deutliche Emissionsabsenkung fuer CO, HC und NOx. Die AU identifiziert Fahrzeuge mit emissionsrelevanten Defekten, die durch Wartung beziehungsweise Reparatur behoben werden und somit die Fahrzeuge auf ein Emissionsniveau zurueckfuehrt, welches in etwa dem des Neuzustandes entspricht. Wuerde die AU entfallen, wuerde der Anteil von Fahrzeugen mit emissionsrelevanten Defekten bis auf ein Saettigungsniveau ansteigen. Bei Abschaffung der bestehenden AU wuerden daher die Jahresemissionen des G-Kat-Kollektivs nach diesen Ueberlegungen um deutlich mehr als die berechnete jaehrliche Reparatur bedingte Emissionsminderung ansteigen. Bericht zum Forschungsprojekt 85.008 (ITRD-Nummer D706796) der Bundesanstalt fuer Strassenwesen. Titel in Englisch: Emissions test - performance study: Spark ignition engines (Otto engines) - three-way catalytic converter. English abstract: Within the scope of this research project 122 vehicles with gasoline engines and three-way catalytic converter, which were conspicuous during the emissions test, were tested extensively. Vehicle selection at the testing facilities was accomplished according to the three primary criteria: Emissions test "not passed" in the areas: - CO at idle speed - CO at increased idle speed - λ at increased idle speed - Regulation circuit test, the volumetric displacement class as well as the year of initial registration. All totalled the selected group of vehicles can be considered to be representative to the greatest extent, because the conspicuity rates were virtually equal in the four criteria in the statistical survey taken in 1997 and in evaluation of the results from the testing facilities. In order to illustrate the effectivity of the emissions test, the defective vehicles were tested on a dynamometer in the state received in three different driving cycles, then repaired in market-related workshops and tested again on the dynamometer after passing the emissions test. Comparison of the emissions before and after repair in the NEFZ cycle indicated a significant emission reduction for CO, HC and NOx on the vehicles studied. The overall reduction of the emissions, achieved by repairing the conspicuous passenger cars equipped with three-way catalytic converter, was calculated for the reference year 1997. In order to evaluate the efficiency of the emissions testing procedure, the calculated reduction in the emissions was placed in relation to the total emissions from the fleet of vehicles with three-way catalytic converter, subject to the emissions test during the reference year. The efficiency of the emissions test was approx. 12% (18%) in terms of HC emissions, approx. 13% (14%) for CO and approx. 6% (7%) for NOx. The values in parentheses refer to a fictive case assuming that the entire operating performance is measured with the engine warmed up to operating temperature. The efficiency of the emissions testing procedure in terms of the CO2 emissions and fuel consumption was negligibly low with a maximum value of 0.2%. The emissions test identifies vehicles with emission-relevant defects, which can be eliminated by service and repair and therefore returns vehicles to an emission level corresponding approximately to the new state. Since there was no control group (vehicles not subject to emissions test), this estimate was made solely on the basis of present experience. If the emissions test were eliminated, the percentage of vehicles with emission-relevant defects would increase up to a saturation level. It is estimated that the conspicuity rate for the group of vehicles with three-way catalytic converter could be 1.5 to 3.5 times higher without the emissions test than the corresponding group of vehicles with catalytic converter with emissions test. If the existing emissions test were discontinued, the annual emissions from the group of vehicles with catalytic converter would therefore increase significantly more, according to these considerations, than by the calculated annual reduction of emissions resulting from repair. (A)
Abstract